using System;
using System.Linq;
using System.Collections.Generic;
using System.IO;
 
public class Test
{
 
	public static void Main()
	{
        string[] fileNames = new[]{"teext_023.ext", "txtxt.x9.08.ext", "text0911.ext"};
List<string> versions = fileNames
            .Select(fileName =>
                Path.GetFileNameWithoutExtension(fileName).Split('_')
                    .Last()
                    .Reverse()
                    .TakeWhile(c => c == '.' || Char.IsDigit(c))
                    .Reverse()
            ).Select(chars => new string(chars.ToArray())).ToList();
            foreach(var strVersion in versions)
                Console.WriteLine(strVersion);
	}
}

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